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WCF版的PetShop之三：實(shí)現(xiàn)分布式的Membership和上下文傳遞
上一篇文章主要討論的是PetShop的模塊劃分，在這一篇文章中我們來討論在一個(gè)模塊中如何進(jìn)行層次劃分。模塊劃分應(yīng)該是基于功能的，一個(gè)模塊可以看成是服務(wù)于某項(xiàng)功能的所有資源的集合；層次劃分側(cè)重于關(guān)注點(diǎn)分離（SoC：Separation of Concern ），讓某一層專注于某項(xiàng)單一的操作，以實(shí)現(xiàn)重用性、可維護(hù)性、可測試性等相應(yīng)的目的。Source Code從這里下載。
一、基本的層次結(jié)構(gòu)
我們接下來將目光聚焦到模塊內(nèi)部，看看每一個(gè)模塊具體又有怎樣的層次劃分。我們將Infrastructures、Products和Orders目標(biāo)展開，將會(huì)呈現(xiàn)出如圖1所示的層次結(jié)構(gòu)。
圖1 從解決方案的結(jié)構(gòu)看模塊的層次結(jié)構(gòu)
以Products模塊為例，它由如下的項(xiàng)目組成：
- Products：對于整個(gè)應(yīng)用來說，Products是最終基于該模塊功能的提供者；
- Products.Interface: 模塊提供給其他模塊的服務(wù)接口，本項(xiàng)目被Products項(xiàng)目引用；
- Products.Service.Interface：模塊客戶端和服務(wù)端進(jìn)行服務(wù)調(diào)用的WCF服務(wù)契約，Products項(xiàng)目最為WCF服務(wù)的客戶端通過該接口進(jìn)行服務(wù)調(diào)用；
- Products.Service：實(shí)現(xiàn)了上述服務(wù)契約的WCF服務(wù)，引用了Products.Service.Interface項(xiàng)目；
- Products.BusinessComponent：也可以稱為業(yè)務(wù)邏輯層，實(shí)現(xiàn)了真正的業(yè)務(wù)邏輯；
- Products.DataAccess：數(shù)據(jù)訪問層，在這里主要提供對數(shù)據(jù)庫的訪問；
- Products.BusinessEntity：提供的業(yè)務(wù)實(shí)體（BusinessEntity）類型的定義。一般來講，業(yè)務(wù)實(shí)體和數(shù)據(jù)契約（DataContract）是不同的，前者主要對本模塊，后者則對外，在這里為了簡單起見，將兩者合二為一。
從部署的角度講，Products和Products.Interface部署與于Web服務(wù)器；Products.Service、Products.BusinessComponent和Products.DataAccess則部署于應(yīng)用服務(wù)器；Products.Service.Interface和Products.BusinessEntity則同時(shí)被部署于Web服務(wù)器和應(yīng)用服務(wù)器。整個(gè)層次結(jié)構(gòu)大體上如圖2所示。
圖2 邏輯層次和物理部署
二、數(shù)據(jù)庫設(shè)計(jì)
整個(gè)應(yīng)用主要涉及4個(gè)表，其中3個(gè)用于存儲業(yè)務(wù)數(shù)據(jù)（產(chǎn)品表、訂單表和訂單明細(xì)表），另一個(gè)用于存儲簡單的審核信息（審核表）。4個(gè)表的結(jié)構(gòu)可以分別參考相應(yīng)的SQL腳本。
產(chǎn)品表（T_PRODUCT）
1: CREATE TABLE [T_PRODUCT] (
2: [PRODUCT_ID] [VARCHAR](50) NOT NULL,
3: [PRODUCT_CATEGORY] [NVARCHAR](128) NOT NULL,
4: [PRODUCT_NAME] [NVARCHAR](256) NOT NULL,
5: [PRODUCT_PIC] [NVARCHAR](512), 6: [PRODUCT_DESC] [NVARCHAR](800),7: [PRODUCT_UNIT_PRICE] [DECIMAL](10,2) NOT NULL,
8: [PRODUCT_INVENTORY] [INT] NOT NULL,
9: 10: [VERSION_NO] [TIMESTAMP] NOT NULL,
11: [TRANSACTION_ID] [VARCHAR](50) NOT NULL,
12: [CREATED_BY] [NVARCHAR](256) NOT NULL,
13: [CREATED_TIME] [DATETIME] NOT NULL,
14: [LAST_UPDATED_BY] [NVARCHAR](256) NOT NULL,
15: [LAST_UPDATED_TIME] [DATETIME] NOT NULL
16: 17: CONSTRAINT [C_PRODUCT_PK] PRIMARY KEY CLUSTERED ( [PRODUCT_ID] ASC ) ON [PRIMARY]) ON [PRIMARY]
系列文章導(dǎo)航：
WCF版的PetShop之三：實(shí)現(xiàn)分布式的Membership和上下文傳遞
四、數(shù)據(jù)訪問層設(shè)計(jì)
數(shù)據(jù)訪問層定義在{Module}.DataAccess中，它完成單純的基于數(shù)據(jù)庫操作。為了便于操作，我寫了一個(gè)簡單的幫助類：DbHelper。DbHelper通過ADO.NET完成一些簡單的操作，ExecuteReader、ExecuteNonQuery和ExecuteScalar對應(yīng)DbCommand的同名方法。此外，該DbHelper與具體的數(shù)據(jù)庫無關(guān)，同時(shí)支持SQL Server和Oracle。
1: using System.Collections.Generic;
2: using System.Configuration;
3: using System.Data;
4: using System.Data.Common;
5: using System.Data.OracleClient;
6: using System.Data.SqlClient;
7: namespace Artech.PetShop.Common
8: {9: public class DbHelper
10: {11: private DbProviderFactory _dbProviderFactory;
12: private string _connectionString;
13: private DbConnection CreateConnection()
14: {15: DbConnection connection = this._dbProviderFactory.CreateConnection();
16: connection.ConnectionString = this._connectionString;
17: return connection;
18: } 19: 20: private void DeriveParameters(DbCommand discoveryCommand)
21: {22: if (discoveryCommand.CommandType != CommandType.StoredProcedure)
23: {24: return;
25: } 26: 27: if (this._dbProviderFactory is SqlClientFactory)
28: { 29: SqlCommandBuilder.DeriveParameters 30: ((SqlCommand)discoveryCommand); 31: } 32: 33: if(this._dbProviderFactory is OracleClientFactory)
34: { 35: OracleCommandBuilder.DeriveParameters 36: ((OracleCommand)discoveryCommand); 37: } 38: } 39: 40: private void AssignParameters(DbCommand command, IDictionary<string, object> parameters)
41: {42: IDictionary<string, object> copiedParams = new Dictionary<string, object>();
43: foreach (var item in parameters)
44: { 45: copiedParams.Add(item.Key.ToLowerInvariant(), item.Value); 46: }47: foreach (DbParameter parameter in command.Parameters)
48: {49: if (!copiedParams.ContainsKey(parameter.ParameterName.
50: TrimStart('@').ToLowerInvariant()))
51: {52: continue;
53: } 54: 55: parameter.Value = copiedParams[parameter.ParameterName.56: TrimStart('@').ToLowerInvariant()];
57: } 58: } 59: 60: public DbHelper(string connectionStringName)
61: {62: string providerName = ConfigurationManager.ConnectionStrings
63: [connectionStringName].ProviderName;64: this._connectionString = ConfigurationManager.ConnectionStrings
65: [connectionStringName].ConnectionString;66: this._dbProviderFactory = DbProviderFactories.GetFactory(providerName);
67: } 68: 69: public DbDataReader ExecuteReader(string procedureName, IDictionary<string, object> parameters)
70: { 71: DbConnection connection = this.CreateConnection();
72: using (DbCommand command = connection.CreateCommand())
73: { 74: command.CommandText = procedureName; 75: command.CommandType = CommandType.StoredProcedure; 76: connection.Open();77: this.DeriveParameters(command);
78: this.AssignParameters(command, parameters);
79: return command.ExecuteReader(CommandBehavior.CloseConnection);
80: } 81: } 82: 83: public int ExecuteNonQuery(string procedureName, IDictionary<string, object> parameters)
84: {85: using (DbConnection connection = this.CreateConnection())
86: {87: using (DbCommand command = connection.CreateCommand())
88: { 89: command.CommandText = procedureName; 90: command.CommandType = CommandType.StoredProcedure; 91: connection.Open();92: this.DeriveParameters(command);
93: this.AssignParameters(command, parameters);
94: return command.ExecuteNonQuery();
95: } 96: } 97: } 98: 99: public T ExecuteScalar(string procedureName, IDictionary<string, object> parameters)
100: {101: using (DbConnection connection = this.CreateConnection())
102: {103: using (DbCommand command = connection.CreateCommand())
104: { 105: command.CommandText = commandText; 106: command.CommandType = CommandType.StoredProcedure;107: this.DeriveParameters(command);
108: this.AssignParameters(command, parameters);
109: connection.Open();110: return (T)command.ExecuteScalar();
111: } 112: } 113: } 114: } 115: } NET技術(shù)：WCF版的PetShop之二：模塊中的層次劃分，轉(zhuǎn)載需保留來源！
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